How is -9 the same as 9? explain

Pls! does anybody know a shortcut for answering these types of questions in the future?

An equation representing lyle’s hedge-trimming business is a = 12n - 300 where a is the amount of profit or loss in dollars and n is the number of hedges trimmed. how would the graph of lyle’s business change if the equation a = 10n - 300 represented his business? the graph would be flatter. the graph would be steeper. the graph would start closer to the origin. the graph would start lower on the y-axis.

60 2(x + 2) in the diagram, gef and hef are congruent. what is the value of x?